Air Water Separator for Compressor

air water compressor
(Last Updated On: March 22, 2020)

I am looking for an air/water seperator for my air compressor. It needs to maintain 120-130psi. I only run 3 main air lines off the compressor. 100gal compressor. can you help me?

We answer…

A few things you should consider.

An air/water separator, also known as an air line filter, doesn’t maintain pressure. It’s purpose is to use cyclonic action and a filter element to strip free water (liquid water) and particulates from the compressed air stream. That’s it.

Most filters will have a delta P (pressure drop) across them of around 5 PSI. So, if you have an upstream pressure of 120 PSI, you’ll get about 115 PSI out the other side of the filter. This is caused by the filter element and filter components restricting the air flow.

As the element gets plugged up, your pressure drop will increase, eventually to the point where you won’t get enough air through the filter to do work.

Check the price of this one HERE

air compressor separator

Some manufacturers of compressed air filters offer an indicator of some sort on their filter housings to show when the element is getting plugged. Having a pressure gage upstream, and another downstream of the air filter would do the same thing…tell you when the pressure drop is increasing, thus indicating that the element is getting plugged.

You indicate that you have a 100 gallon compressor. What you have is a 100 gallon tank. Except for reservoir capacity, the tank size tells me nothing about the compressor. You need to identify the horsepower of the motor. That can be converted (approximately) into CFM, and it’s the CFM number you need to ensure that a new filter has the capacity for your air line.

All of the 3 air lines emanating from your compressor discharge outlet should be supplied through a main compressed air filter. Then, you will want to put another (smaller) air filter at the point of use for each air line. That will strip more free water (it condenses in the air lines) and any additional particulate from the compressed air before it gets to your tools or applications.

While it’s not foolproof, particularly in high demand applications, since most general purpose filters provide around a 25-40 micron element, you can roughly size the filter by getting them with the port size being the same size as the supply line. For example, a 3/4″ pipe air line should be fitted with a 3/4″ NPT ported filter…and so on.

Much more information about air filters is here.



Hello, I am Bill, the Compressed-Air-Man. I have years of experience in industrial and residential compressed air applications, air compressors and general pneumatics. I created this site to help professionals, students, and DIYers understand and properly implement and maintain compress3ed air systems.


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